Name __________________________ Date __________ Period ____ Due _________
Regents Biology Laboratory Investigation
SEED GERMINATION AND
GROWTH
Background Information
In order to be alive, we know that an organism must perform each one of the eight
life processes, with the possible exception of reproduction, which is a species process.
That means that while not every member of a species must reproduce, at least some have
to, or the species would become extinct. There are, however, myriad ways to be alive,
like being an animal, a plant, a fungi, bacteria, or a protist. Today, we will examine how
“baby” plants behave.
Plants start out from seeds. These seeds must sprout into mature plants, but to do
so they must accomplish some pretty amazing feats. It must figure out which way is up,
and once it has done that, figure out how to make a shoot grow in that direction, and how
to get roots to grow in the opposite direction. Then it’s got to start transporting the
proper amount of water, make sure that its ion concentration is ok, produce flowers or
fruit, and perhaps go dormant for the winter. It must do all this without the aid of a
nervous system! How, then, does the plant “tell” certain parts to become shoots, leaves,
or roots?
The answer lies in hormones. Plants have many hormones, but one of the most
important one is called auxin. Auxin causes the elongation of cells, and is responsible for
many of the tropisms that we see in plants. For example, phototropism is the growth of a
plant towards a light source. The plant accomplishes this by moving auxin away from the
side with the light source, and towards the dark side. This causes the cells on the darker
side to extend, pushing the plant towards the light.
Gravitropism is the movement of a plant towards gravity. Auxin is involved in
this, as well. Though the complete mechanism is unknown, auxin is transported to the
bottom of a plant, which causes roots to grow there. Plants may also sense gravity by the
use of organelles known as statoliths. These are large plastids filled with starch, which
settle to the bottom of the plant’s cells, because they are denser than the cytoplasm.
Finally, Thigmotropism is the ability of a root or stem to grow around an object.
Little is known about this property of plants, such as when a cucumber stem grows
around a trellis, but it is believed to involve auxin as well.
Yet another hormone involved in plant growth is gibberellin. This hormone
causes elongation of stems, and can also promote fruit production, flowering, or control
the transition from the juvenile to adult stages.
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Purpose
The purpose of this investigation is to discover how plant roots and shoots
develop in the proper directions, and also to explore the effects of two important
hormones on plants. You will also see many of the main structures that are present in
germinating and growing plants.
Materials
Bean seeds
PENCIL
Paper towels
Scissors
Masking tape
Gibbberellic acid
Droppers
Petri dish
Dissecting pins
Cardboard
Sammich bag
Marker
Auxin
Beakers
Procedure
PART I – PREPARATION OF SEEDS
1. Select a few seeds from the lab bench; it does not matter which you use.
2. Cut a piece of cardboard about 13 cm wide and about 26 cm long.
3. Fold the cardboard in half, to make a tent. Staple several paper towels to the
outside of the tent.
4. Place the tent in your Petri dish, and label your dish with your group member’s
names.
5. Using the dissecting pins, pin several seeds to each side of the tent. Place them
in the middle, not towards the bottom or top.
6. Moisten the paper towels with water, and fill the Petri dish about half way with
water.
7. Place the sammich bag over the entire contraption to create a little greenhouse.
8. Use the droppers to keep the Petri dish full. Check it once a day.
PART II – ADD HORMONES
1. Once your seeds have germinated, select a hormone to add, and decide where
you want to add it. You may choose to add it to the entire growing plant, just the roots,
just the shoots, one side of the roots, etc. Try many different applications on your many
seeds! Record what you are going to do in table 1. You may want to number your seeds
using tape or another pin to make them easier to identify. Take care not to rotate them or
nudge them out of place when working with your seeds.
2. Make a hypothesis, based on what you know about plant hormones, describing
what you think will happen to the various seeds.
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Seed Number
Hormone
Location
Notes
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2
3
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Table 1. Hormone application to various seeds
QUESTION 1: Make a hypothesis about what you think will happen to your various
seeds with the various hormones applied.
3. In table 2, keep track of the growth of your seeds. Also describe any other
changes that might be occurring.
Day
Height
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2
3
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5
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7
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Observations
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Table 2. Height and observations over time for various treated seeds.
Analysis
QUESTION 2: What does auxin do to plant cells?
QUESTION 3: Gibberellin was originally discovered in Japanese rice plants with a
disease called bakanae, or “foolish seedling” disease. This is because the seedlings grew
so fast that they fell over. What role did gibberellin play in this disease?
QUESTION 4: What is one way that hormones might move around inside a plant?
QUESTION 5: Did it matter which way your seed was placed on the tent? That is, did
the root always grow down and the shoot always up?
QUESTION 6: Why do you think that you might observe so many tiny hairs on the sides
of the main roots?
QUESTION 7: If you could change two things about this lab, what would they be?
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